Hydrogenation of higher fatty acids



Patented Aug. 16, 1938 T HYDROGENATION OF HIGHER FATTY ACIDS Wilhelm Norman and Gustav von Schuckmann, Chemnitz, Germany, assignors to H. Th. Bohme Aktiengesellschaft, Chemnitz, Germany, a

notation of Germany No Drawing. Application November 10, 1934, Serial No. 752,470. In Germany November 18,

9 Claims.

This invention relates to the production of aliphatic esters of fatty acids ofthe nature of waxes and to the production of higher molecular unsaturated alcohols from unsaturated fatty acids.

Prior to the present invention it was discovered that aliphatic alcohols could be'obtained through hydrogenation of fatty acids by a conversion of the carboxyl groups to hydroxyl groups. In such reactions as heretofore practiced; where unsaturated fatty acids were treated, hydrogen com-' bined at the double bonds with the result that substantially only saturated alcohols were obtained.

Inasmuch as unsaturated alcohols have several properties making them more desirable in certain arts than the corresponding saturated alcohols, a primary object of the present invention is to produce unsaturated fatty alcohols.

A further object of the invention is to produce unsaturated wax esters and also saturated wax esters in high or commercial yields.

In the prior hydrogenation procedure above described, wax esters, but only those of the saturated type, could be obtained in a very poor yield by interrupting the hydrogenation before the reduction to alcohols is complete, such esters being obtained by reaction of a portion of the alcohols formed with a portion of the fatty acids existing in the mass.

We have now discovered that by a suitable regulation of the activity of the catalyst, the catalytic reduction of fatty acids may be so directed and controlled that wax-esters are obtained as the main portion of the product, and that when utilizing unsaturated fatty acids as raw material, the unsaturated character can, if desired or necessary, for the most part be retained. The process therefore, makes possible the production of unsaturated wax-esters and the production of unsaturated alcohols by the saponification of these unsaturated esters.

. Heretofore, it was possible to convert fatty acids into unsaturated alcohols only by the complicated method using sodium and alcohol. The process of the invention hence opens up new methods for the inexpensive, large-scale production of the unsaturated fatty alcohols from vegetable, and animal fats, oils and waxes, available in great amounts in this country, such as oleins and the like, while heretofore sperm-oil, which must be imported from foreign countries was the principal source of raw material for these unsaturated alcohols, especially oleyl alcohol.

The present-invention is applicable to the production of esters from aliphatic carboxylic acids in general, but is especially adapted to the preparation of esters of wax like character from fatty acids having 8 or more carbon atoms in the molecule.

In accordance with one specific embodiment of theinvention, the activity of the catalyst may be regulated by incorporation of the regulating element or compound such as sulfur in an organic solvent with which the same may be reacted wholly or in part, a suitable solvent being xylene in admixture with quinoline. When such sulfur and solvent mixture is employed, it is advantageous. to heat the mixture for a. prolonged period until a copious quantity of hydrogen sultide is generated, which gas indicates that partial substition occurs.

As an example in detail of a satisfactory methed of preparing sulfur for the regulation operation, 6 parts of sulfur are boiled for seven hours in 36 parts of quinoline, after which the sediment is filtered 0d and the liquid diluted with 400 c. c. of xylene. It should be understood that other solvent mixtures may be employed and also that the present invention is not limited to the use of solvents together with the regulator.

Instead of sulfur, other compounds and elements may be used, namely, cyanogen compounds, phosphorus, carbon monoxide, and ar-v senic compounds. A

' Example 1 which requires about 30 minutes, whereby the pressure rises to 200 atmospheres or more. It is kept for a further 15 minutes at 280 (3.. then allowed to cool, after which the hydrogen is vented off. One obtains a product which shows the fol- I,

lowing characteristic figures:

Acid number 58.3

Iodine number 5.6 Hydroxyi number ill Ester number 83.4

The ester number of 83.4 corresponds to a content of 80.8 per cent of ester.

In contrast thereto, with the omission of the regulator other conditions being unchanged, one i obtains a product with the following characteristic results:

The ester number of 33.3 corresponds to a content of only 32.2 per cent of ester.

Example 2 25 parts by weight of oleic acid, together with 2.5 parts by weight of a copper-chromium catalyst and with the addition of an amount of regulator which amounts to 0.62 per cent of sulfur, calculated on the weight of the catalyst, are introduced into the autoclave, hydrogen being forced in until a pressure of 150 atmospheres (gage) is reached. This mass is gradually heated up until the temperature of 280 C. has been reached and is then maintained for a further 3 hours at this temperature. It is allowed to cool off and the hydrogen blown off. One obtains a product having the following characterizing figures:

The ester number of 76.9 corresponds to a content of ester of 74.5 per cent.

The copper-chromium catalyst used may be prepared, for example, as follows:

2.5 kgs. of a copper sulfate are dissolved in 8 liters of water, precipitated at 90, C. with a solution of 1.42 kgs. of calcined soda in 4 liters of water. The copper carbonate is washed and filtered and is thereupon again suspended in 2 liters of water. The suspension is then treated at the boiling temperature with a solution of 840 grams of ammonium dichromate in 3 liters of water. The precipitate is washed, dried, and roasted at 400 C.

In place of the copper-chromium catalyst, use may also be made of any one or combination of the large number of other known hydrogenationcatalysts, such as platinum, palladium, cobalt, and nickel catalysts, as well as mixtures of the enumerated catalytic substances, also the known methanol-catalysts, and the like, physical mixtures and chemical mixtures and oxides of such metals being included.

The present invention is independent of the particular temperatures and pressures employed, for the reason that the conditions which will produce alcohols are already known and these conditions are in general the same for the production of the esters of the instant invention. The preferred range of temperatures is however in general 200 to 400, and of pressure of from 100 to 500 atmospheres.

The amounts of regulator for other catalysts,

or of regulating substances other than sulfur, can be easily determined by means of a few preliminary experiments.

We claim:

1. In the catalytic reduction of fatty acids at elevated temperatures and pressures in the presence of hydrogen, the step of regulating the activity of the catalyst by means of a catalyst poison in such manner that the reduction of the carboxyl radical alone is effected and not ester radicals resulting from reaction of the alcohols produced with fatty acids.

2. The process of producing wax'esters comprising catalytically reducing fatty acids at elevated temperatures and pressures adapted to reduce fatty acids to the alcohol stage in the presence of hydrogen and a catalyst poison selected from the group consisting of sulfur, phosphorus, compounds of such elements and carbon monoxide.

3. The process of producing unsaturated alcohols, comprising catalytically reducing unsaturated fatty acids at elevated temperatures and pressures adapted to reduce fatty acids to the alcohol stage in the presence of hydrogen and a substance selected from the group consisting of sulfur, phosphorus, compounds of such elements and carbon monoxide, and saponifying the resulting' esters of unsaturated alcohols.

4. The process of producing wax esters comprising catalytically reducing fatty acids at elevated temperatures and pressures adapted to reduce fatty acids to the alcohol stage in the presence of hydrogen and a sulfur compound.

5. The process of producing wax esters comprising catalytically reducing fatty acids at elevated temperatures and pressures adapted to reduce fatty acids to the alcohol stage in the presence of hydrogen and a small proportion of sulfur.

6. The process of producing wax esters comprisingreducing a higher fatty acid by heating such acid to an elevated temperature and pressure adapted to reduce fatty acids to the alcohol stage in the presence of a hydrogenation catalyst and a catalyst poison adapted to limit the hydrogenation to the free carboxyl groups contained in the mass.

7. The process as described in claim 6, wherein the catalyst is a copper-chromium catalyst.

8. The process as described in claim 6, wherein the catalyst is a copper-chromium catalyst, and the catalyst poison is sulfur.

9.. The process as described in claim 6, wherein the catalyst is a copper-chromium catalyst, the catalyst poison is sulfur and the fatty acid treated is unsaturated whereby esters containing unsaturated alkyl radicals are obtained.

WILHELM NORMANN. GUSTAV V. SCHUCKMANN. 

